In a wireless communications system, data transmission includes uplink transmission and downlink transmission. Uplink transmission refers to that user equipment (UE for short) sends data to a base station, and downlink transmission refers to that the base station sends data to the UE. In addition, different time and frequency resources need to be occupied in uplink transmission and downlink transmission. For example, in a Long Term Evolution (LTE for short) system that uses a time division duplex (TDD for short) manner, in uplink transmission and downlink transmission, frames within different time intervals need to be occupied for data transmission.
In an LTE system, a frame may be divided into ten frames, and the ten frames include an uplink subframe, a downlink subframe, and a special subframe. Each subframe may be further divided into multiple symbols in time, where the multiple symbols may be orthogonal frequency division multiplex (OFDM for short) symbols or single carrier frequency division multiple access (SC-FDMA for short) symbols. The OFDM symbol is used for downlink transmission, and the SC-FDMA symbol is used for uplink transmission.
In the prior art, as shown in FIG. 1, two consecutive subframes are included, that is, a subframe n and a subframe n+1. A first symbol of each subframe is allocated as an OFDM symbol, and the first symbol is used to transmit a downlink control channel. A second symbol is allocated as an SC-FDMA symbol, and the second symbol is used to transmit an uplink control channel. A remaining symbol following the second symbol may be allocated as an SC-FDMA symbol, or may be allocated as an OFDM symbol. Therefore, the remaining symbol following the second symbol is used to transmit uplink data or downlink data. In addition, a particular guard period is needed when a network device switches between uplink transmission and downlink transmission. The network device cannot transmit data within the guard period. Therefore, for two consecutive symbols, if one symbol is used for uplink transmission and the other symbol is used for downlink transmission, that is, one symbol is an SC-FDMA symbol and the other symbol is an OFDM symbol, a guard period needs to be set between the two symbols. As shown in FIG. 1, two times of switching between uplink transmission and downlink transmission need to be performed within each subframe, and three guard periods need to be set.
Although such existing design is relatively flexible, the design has shortcomings of resource wasting and complex implementation. Specifically, in the prior art, three guard periods need to be set in one subframe. As a result, not only effective data information cannot be sent within a time of a guard period, but also a communications device needs to frequently switch between receiving and sending states, causing an increase in implementation complexity.